Get Shark to compile with latest Spark master.
Handle SparkHadoopWriter being made non-pubic.

Added a simple CreateJobID() nested function
Revert to using RDD#collect() for map joins,
Since Spark can send Task results through the block manager when the Akka frame size is exceeded

- Reverts Shark PR #98
- Relevant commit on the Spark side: apache/incubator-spark@c75eb14
Catch exceptions thrown by threads launched in ScriptOperator.
Synchronize calls to TaskContext#addOnCompleteCallback() in ScriptOperator.
Remove Kryo references in SharkEnv. The ShuffleSerializer is explicitly specified as the object serializer for shuffle ops.
Add a NULL check in ReduceKeyReduceSide#equals().
Compatible with Spark-0.8.1-incubating-SNAPSHOT @3db505c21f
SNAPSHOT version for Spark